Flash spinning process

Abstract

A spinning process using azeotropic compounds as spin agents having essentially zero ozone depletion potential and that are either non-flammable or of very low flammability.

What is claimed is: 
     
       1. A process for the preparation of plexifilamentary film-fibril strands of synthetic fiber-forming polyolefin which comprises flash-spinning at a pressure that is greater than the autogenous pressure of the spin fluid into a region of lower pressure, a spin fluid comprising (a) 5 to 30 wgt. % synthetic fiber-forming polyolefin, and (b) a spin agent selected from the group consisting of an azeotropic mixture of about 46 wgt. % decafluoropentane, about 40 wgt. % trans-1,2 dichloroethylene and about 14 wgt. % cyclopentane; and an azeotropic mixture of about 50 wgt. % perfluorobutyl methyl ether and about 50 wgt. % trans-1,2-dichloroethylene. 
     
     
       2. The process of claim 1, wherein the synthetic fiber-forming polyolefin is selected from the group consisting of polypropylene and polymethylpentene. 
     
     
       3. The process of claim 2, wherein the polypropylene is present in an amount of 6 to 15 wgt. %. 
     
     
       4. The process of claim 2, wherein the polymethylpentene is present in an amount of 8 to 20 wgt. %. 
     
     
       5. A process for the preparation of microcellular foam fibers from a synthetic fiber-forming polyolefin which comprises flash-spinning at a pressure that is greater than the autogenous pressure of the spin fluid into a region of lower pressure, a spin fluid comprising (a) at least 40 wgt. % synthetic fiber-forming polyolefin, and (b) a spin agent selected from the group consisting of a mixture of about 46 wgt. % decafluoropentane, about 40 wgt. % trans-1,2 dichloroethylene and about 14 wgt. % cyclopentane; and a mixture of about 50 wgt. % perfluorobutyl methyl ether and about 50 wgt. % trans-1,2-dichloroethylene. 
     
     
       6. The process of claim 5, wherein the synthetic fiber-forming polyolefin is selected from the group consisting of polypropylene, polymethylpentene, partially fluorinated copolymers of ethylene and tetrafluoroethylene and partially fluorinated copolymers of ethylene and chlorotrifluoroethylene. 
     
     
       7. The process of claim 6, wherein the synthetic fiber-forming polyolefin is present at between about 40 and 60 wgt. %. 
     
     
       8. The process of claim 5, wherein the spin fluid comprises nucleating agents selected from the group consisting of fumed silica and kaolin. 
     
     
       9. The process of claim 5, wherein the spin fluid comprises low boiling inflating agents selected from the group consisting of hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroethers, perfluorocarbons, butane, isopentane, carbon dioxide and nitrogen. 
     
     
       10. A process for the preparation of plexifilamentary film-fibril strands of synthetic fiber-forming polyolefin which comprises flash-spinning at a pressure that is greater than the autogenous pressure of the spin fluid into a region of lower pressure, a spin fluid comprising (a) 10 to 40 wgt. % of a synthetic fiber-forming polyolefin selected from the group consisting of a partially fluorinated copolymer of ethylene and tetrafluoroethylene and a partially fluorinated copolymer of ethylene and chlorotrifluoroethylene and (b) a spin agent selected from the group consisting of a mixture of about 46 wgt. % decafluoropentane, about 40 wgt. % trans-1,2 dichloroethylene and about 14 wgt. % cyclopentane; and a mixture of about 50 wgt. % perfluorobutyl methyl ether and about 50 wgt. % trans-1,2-dichloroethylene.